ipopolysaccharide (LPS) comprises about 40% of the ram-negative outer membrane (OM). Due to its biochemical omposition and surface location, LPS mediates a number of mmune and nonimmune host responses. Analysis of the structure nd function is essential for understanding the role of LPS in he pathogenesis of disease. This is a multifocal project with wo basic themes: (A) Development of reagents and techniques or use in evaluating bacterial LPSs, and (B) Analysis and omparison of LPSs of pathogenic bacteria. Specific aspects of his project include first, development and analysis of DS-PAGE as a tool for fingerprinting LPSs, this necessitates dentification of the catalog of artifacts influencing the ehavior of LPS migration: pH as well as SDS concentration are ritical components in mediation of aberrant LPS migration. nalysis of SDS-PAGE/immuno-electroblotting techniques for robing the antigenicity of LPS demonstrates steric factors arkedly affect epitopes available for antibody binding. econd, analysis of the chick embryo model as a bioassay for PSs, the chick embryo assay is unique in that the toxic rinciple is not lipid A. The LPSs of two intracellular athogens are nontoxic in this bioassay. Third, LPSs of three enereal pathogens are being analyzed and compared. These LPSs re similar in that O antigens are absent. The LPS of eisseria gonorrhoeae is heterogeneous depending upon the train, no heterogeneity has been detected within a given train with respect to piliation or opacity phenotype. The LPS f Chlamydia trachomatis L2 (LGV strain) has also been solated; like the LPS of N. gonorrhoeae, it too cross-reacts ith antisera made to Salmonella lipid A and Re LPS. However, he LPS of C. trachomatis is nontoxic in the chick embryo ssay. The rough LPS of Contagious Equine Metritis Organism CEMO) also cross-reacts with antibodies to lipid A but not ith antibodies directed against Re LPS. This is consistent ith the absence of KDO in the TBA assay. Fourth, the ssociation of LPS with OM protein constituents (protein I and ili) is being examined.